Fluorocyclohexyl amine compounds



Patented 6 i949 E CDMIPQNINDS Joseph H. Simona, State College, Pa,assignor to Minnesota Mining & Manuiacturlng Company, St. Paul, Minn, acorporation oi Delaware No Drag. Application July 314, 1948, Serial No.38,752

This application relates to the discovery of a new and useful class ofsynthetic cyclic carbon compounds which contain only nitrogen andfluorine in addition to carbon.

More specifically, this application relates to the discovery oftridecafluorocyclohexyl amine, CcFuNFz, a cyclic compound having aG-carbon ring and a single nitrogen atom which is bonded to one carbonatom of the ring and to two fluorine atoms. The structural formula is:

has a boiling point of about 77 C.

This compound corresponds to cyclohexyl amine, CeHuNHa, the hydrogenatoms thereof being entirely replaced by fluorine atoms. The presentcompound has a much lower boiling point, since the boiling point ofcyclohexyl amine is 134 (3.; despite the fact that its molecular weightis 333, whereas that of cyclohexyl amine is 99. Cyclohexyl amine is aprimary amine and may be regarded as derived from ammonia, NH3, byreplacement of one hydrogen atom by a hydrocarbon radical. The presentcompound should be regarded as derived from NFa, by replacement of onefluorine atom by a fluorocarbon radical, and cannot properly be classedas an amine, despite the name given to it as a matter of expediency inaccordance withrecognized nomenclature practice.

The present invention also includes higherboiling homologous compoundswherein a saturated fluorocarbon side group or chain, having the formula-CnF2n+1, is bonded to a carbon atom of the ring, replacing a fluorineatom. These correspond to the C-alkyl cyclohexyl amine compounds, thehydrogen atoms being replaced by fluorine atoms. Examples of suchhomologous compounds are: CFaCsFmNFz, pentadecafluoromethylcyclohexylamine, corresponding to methylcyclohexyl amine; CzFsCsFloNFz,heptadecafluoroethylcyclohexyl amine, corresponding to ethylcyclohexylamine; CaFaCsFwNFz, nonadecafluoropropylcyclohexyl amine, correspondingto propylcyclohexyl amine; CQFSCGFNNFZ, heneicosafluorobutylcyclohexylamine, corresponding to butylcyclohexyl amine; CsFnCsFmNFz,tricosafluoroamylcyclohexyl amine, corresponding to amylcyclohexylamine; CcFraCcFroNFz,

CnFanuCcFmNFa where n is zero or an integer.

The compounds of this invention have physical properties resemblingthose of the saturated fluorocarbons (carbon fluorides). They have ahigh degree of thermal stability, exceptionally low boiling pointsrelative to molecular weight, low refractive indices, low dielectricconstants, low viscosities and low surface tensions. They may beemployed as solvents, hydraulic mechanism fluids and dielectrics. Unlikethe fluorocarbons (wherein the fluorine atoms are all bonded to carbonatoms), the present compounds contain two nitrogen-bonded fluorine atomsin the molecule in consequence of which the molecule is reactive. Theyare able to enter into various chemical reactions so as to have value aschemical intermediates in the production of other compounds, the NF:group and either or both of the N-bonded fluorine atoms beingreplaceable by other atoms and radicals.

The electrochemical process broadly described and claimed in mycopending application, Ser. No. 677,407, filed June 17, 1946, (sinceabandoned in favor of Ser. No. 62,496, filed November 29, 1948), may beemployed in preparing compounds of this invention. Briefly, this processinvolves electrolyzing in liquid hydrogen fluoride a correspondinghydrogen-containing starting compound, having the same or a similarskeleton structure as that of the desired product compound. Thuscyclohexyl amine, CcHuNHz, can be used as the starting compound formaking tridecafiuorocyclohexyl amine, CsFuNFz. Also, it is possible touse the corresponding aromatic hydrogen-containing compound as thestarting compound, in which case the process causes fluorine addition aswell as hydrogen replacement to produce the saturated product compound.Thus aniline, C6H5NH2, can also be used as the starting compou formaking CoFuNFa, as illustrated in the su sequent example.

The electrochemical process also produces a saturated cyclicfluorocarbon compound having the same number of carbon atoms as thestart ng compound, resulting from breaking of the N-C bond. Thusdodecafluorocyclohexane, CsFis, as

well as CeFiiN'Fz is produced by electrolyzing cyclohexyl amine oraniline. There are also produced various fluorocarbon fragmentationproducts containing fewer carbon atoms than the starting compound. NFais formed. Separation can be effected by fractional distillation.

A simple type of electrolytic cell can be used, employing a nickel anodeand an iron or steel cathode, for example. An iron or steel containercan be used, which may be employed as a cathode,:

with a cover of iron or steel which is bolted in place. Anode andcathode plates, in alternating array, can be suspended from the cover. Asuitable gasket material, and insulating material for electrodemountings and leads, is Teflon" (polytetrafluoroethylene). An upperoutlet for gaseous products, an upper inlet for charging materials, anda bottom outlet for liquid products, may be provided. The cell may beprovided with a cooling jacket for maintaining a desired operatingtemperature.

Commercial anhydrous liquid hydrogen fluoride can be used. This normallycontains a trace of water, but water need not be present and highlyanhydrous hydrogen fluoride can be used. The starting compounds aresoluble in the liquid hydrogen fluoride and provide adequateelectrolytic conductivity.

A cell potential of about 4 to 8 volts has been found suitable, Acurrent density of 20 or more amperes per square foot of anode surfacecan readily be obtained. Voltages sufficiently high to result in theformation of free fluorine are avoided. The process does not depend uponthe generation of free fluoride and the latter, if produced, wouldresult in explosions, electrode corrosion, and undesirable reactions.

.A preferred operating pressure is atmospheric pressure and a preferredoperating temperature is about (3., but higher-and loweroperatingpressures and temperatures can be employed.

The constituent compounds of the gaseous and liquid product mixtures canbe separated by frac tional distillation.

Eremple This example illustrates the making of (LsFuNFz,tridecafluorocyclohexyl amine, using aniline as the starting compoundand employing the previously described electrochemical process.

Use was made of a small iron laboratory cell having a nickel anode,operating at atmospheric pressure and a temperature of 0 C. The cell wasinitially charged with about 650 grams of anhydrous liquid hydrogenfluoride and about grams of anhydrous aniline. During the run additionalaniline was added to maintain the current flow, the total being about 90grams. The average cell voltage was 5.5 volts D. C. The run duration wasabout 200 hours and a total of 14 faradays of current was passed. Themixture of gaseous products evolved from the cell was led through atrain consisting of a tube packed with sodium fluoride, a sodiumhydroxide bubbler, a sulfuric acid bubbler (drier), and a trap cooled bysolid --CO2. The condensate from the latter was subjectedto fractionaldistillation and there was obtained a liquid fraction which wasidentified as relatively pure CsFnNFz, tridecafluorocyclohexyl amine,having the following measured properties:

The values calculated from the formula of the pure compound are:molecular weight, 333; per cent F, 74.2.

There was also obtained a fraction identified as the cyclic fluorocarbonCaFm, dodecafiuoro- 2. The new and useful cyclic compounds of the classconsisting of tridecafluorocyclohexyl amine and of fluoroalkylcyclohexylamines which have the formula:

where n is in integer.

JOSEPH H. SIMONS.

REFERENCES QE'KED The following references are of record in the file ofthis patent:

Reprint, "Fluorine Chemistry Chem., March 1947) pp. 359-434.

(Ind. Eng.

